The mechanisms of [URE3] prion elimination demonstrate that large aggregates of Ure2p are dead-end products

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Ripaud, Leslie | Maillet, Laurent | Cullin, Christophe

Edité par CCSD ; EMBO Press -

International audience. The yeast prion [URE3] is a self-propagating inactive form (the propagon) of the Ure2 protein. Ure2p is composed of two domains: residues 1±93Ðthe prion-forming domain (PFD)Ðand the remaining C-terminal part of the protein, which forms the functional domain involved in nitrogen catabolite repression. Guanidine hydrochloride, and the overproduction of Ure2p 1±65 or Ure2±GFP have been shown to induce the elimination of [URE3]. We demonstrate here, two different curing mechanisms: the inhibition of [URE3] replication by guanidine hydrochloride and its destruction by Ure2p aggrega-tion. Such aggregation is observed if PFD or Ure2± GFP are overproduced and in heterozygous URE2/ URE2±GFP, [URE3] diploids. We found that the GFP foci associated with the presence of the prion were dead-end products, the propagons remaining soluble. Surprisingly, [URE3] propagated via the Ure2±GFP fusion protein alone is resistant to these two curing mechanisms and cannot promote the formation of foci. The relationship between aggregation, prion and Hsp104 gives rise to a model in which the propagon is in equilibrium with larger aggregates and functional protein.

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